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Implementation and Analysis of Single Scattering Models for Hair

Implementation and Analysis of Single Scattering Models for Hair. Student : Javier Meseguer de Paz Supervisor: Jan Kautz. Context. Hair simulation Modelling Animation Rendering Single scattering Multiple s cattering Shadows Other effects Data acquisition and capture.

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Implementation and Analysis of Single Scattering Models for Hair

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  1. Implementation and Analysis of Single ScatteringModelsforHair Student: Javier Meseguer de Paz Supervisor: JanKautz

  2. Context • Hairsimulation • Modelling • Animation • Rendering • Single scattering • Multiplescattering • Shadows • Othereffects • Data acquisition and capture

  3. Mostimportantworks • Kajiya • Firstshadingmodelforhair (actuallyfur) • Marschner et. al. • Firstphysically-basedshadingmodelforhair • Nguyen and Donelly • First real-time implementation of Marschner • Zinke • First formal mathematicalframeworktostudy and generatehairshadingmodels

  4. Goalsof theproject Zinkedid Zinkedidnot Derive Marschner’smodelusinghisframework Hint a more general modelcouldbeused in real-time Explaineverystep in detail Derive themodel Implementthemodel Compare theresults

  5. Goalsof theproject So we: • Explaineverystep in detail • Derivedthemodel • Implementthemodel • …and theothers • Compare theresults

  6. Framework • A precise notationis set

  7. Framework • Twokind of functions are defined: • Modelseverydetail • Requiresfiberwidthlessthan a pixel • Suitablefor real-time rendering • Itispossibletoconvertthe BFSDF into BCSDF

  8. Framework • To derive models, westartwiththe BFSDF forperfectcylinder R TRT interior: refrac. indexn absoprtions TT

  9. Framework • Then, wemodifyitto match hair’smodel - Marschner

  10. Framework • Then, wemodifyitto match hair’smodel- Zinke

  11. Framework • And weconvertfrom BFSDF to BCSDF • In Marschnermodelintegrals can besolved • In the case of Zinkeonlysimplified a little:

  12. Implementation • We pre-compute themodeloffline: Numericalintegrationforthese Cachingtospeed-up this

  13. Implementation • And storeitintofloating-pointtextures: • Then, in real-time, wejusthavetolookup

  14. Results

  15. Results

  16. Results

  17. Comparison • Complexity • Kajiyaistheeasiest (it’sjust a shader!) • Marschneris quite complex • Zinkeeven more! (numericalintegrationinvolved)

  18. Comparison • Speed • Kajiyadoesn’thave pre-computation • Marschneris2500 times fasterthanZinkeonaverage

  19. Renderedimages • Kajiya looks quite good • Marschner and Zinke are essentiallythesame

  20. Conclusions • Itispossibleto derive and implement a real-time version of Zinkemodel • However, itisnotreally a goodchoice • Kajiya has a verygoodquality/complexitytrade-off • Marschner looks goodbutdefinitelyneedsshadowingto show itspotential

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